Is a classical description of nuclear motion sufficient when describing
chemical reactions? The present paper investigates some phenomena that
were previously attributed to nuclear quantum effects. The aim is to
show that these phenomena can be modelled with traditional
Car-Parrinello molecular dynamics, that is, with a method which treats
nuclear motion classically. We find that no additional paradigm is
needed for describing chemical reactions. The special reactivity
observed for carbenes can be attributed to the special environment
represented by a noble gas matrix. Also the infrared spectrum of
porphycene is perfectly modelled by traditional Car-Parrinello molecular
dynamics. If no more convincing examples are produced, one will stick to
deterministic quantum mechanics, as it is the simpler theory which, in
addition, is free of paradoxa.